British Rail locomotive and multiple unit numbering and classification

In 1948, BR inherited a variety of locomotives and multiple units from the Big Four railway companies and some smaller concerns. Details of the numbering and classification systems used by the Big Four companies are covered in the following pages:

• Great Western Railway: GWR locomotive numbering and classification
• Southern Railway: SR locomotive numbering and classification and SR multiple unit numbering and classification
• London, Midland and Scottish Railway: LMS locomotive numbering and classification
• London and North Eastern Railway: LNER locomotive numbering and classification

In the main, new locomotives and multiple units built by BR to pre-nationalisation designs were numbered and classified according to the principles applied by the relevant Big Four company.

Immediately after nationalisation, BR had to decide how to number and classify the stock it had inherited from the Big Four companies, and how newly built stock would be included. In the main, it decided to simply adapt what was already there.

In the early period of British Railways, steam locomotion had continued to be of prime importance. Apart from a growing selection of diesel shunters, there had been almost no development of mainline diesel or electric traction beyond the few locomotives ordered by the Big Four companies.

The 1955 Modernisation Plan heralded big changes in this situation, and from 1957 a new numbering system was used for diesel and electric locomotives ordered by British Railways, including those shunters ordered before 1957, which were renumbered into the new system. All steam and gas-turbine locomotives, and diesel and electric locomotives built to pre-nationalisation orders retained their existing numbers under the 1948 arrangements, though some had a 'D' or 'E' prefix added to their number in error.

At the end of the 1960s, British Rail adopted the Total Operations Processing System (TOPS), a computerised system developed by IBM, the Southern Pacific Transportation Company and Stanford University in the United States. All types of locomotive received a TOPS classification,[3] and multiple units were later included according to this broad division:

From late 1970, British Rail started to apply new numbers to locomotives and multiple units based on the TOPS classification system, the first classes to be dealt with being the LNER-design EM1 type (TOPS class 76) and the AL3 and AL4 types of AC electric locomotives (TOPS classes 83 and 84). The format of these numbers is xxxyyy, where xxx is the class number and yyy the unique identifier for that locomotive or unit. All locomotive classes have unique identifiers that commence at xx001, except classes 43 (High Speed Train power cars, originally classified as multiple-unit vehicles), 97 and 98 (departmental and steam locomotives). Multiple unit classes are treated differently, because an attempt has been made to give units working within the same region or sector unique identifiers (for more information see British Rail Regional Multiple Unit Numbering). In recent years, unit numbers have also been tied in with the numbers of the carriages within a unit (e.g. 150201 is formed of carriages 52201 and 57201). As a result, very few multiple unit classes commence from xxx001.

Where there are variations within a class, subclasses are used in the format xxx/y. When the main renumbering scheme was published in 1973, many sub-classes were redesignated to better align the locomotives to be numbered in that sub-class with the sub-class number. Thus, class 47 was originally divided into sub-classes 47/1 (locomotives fitted with steam-heating equipment), 47/2 (not fitted with train-heating equipment) and 47/3 (fitted with electric train-heating equipment), but in 1973 these sub-classes were redesignated 47/0, 47/3 and 47/4. Usually, the subclass is connected to the first digit of the unique identifier, so that the first locomotive in subclass 47/3 was 47301. However, some caution is required on this point for the following reasons:

• Where there are more than 100 examples in a subclass the identifier becomes obscured, e.g. 31201 is in subclass 31/1, which runs from 31101 to 31327.
• Some classes renumbered from the 1957 arrangements simply had consecutive numbers from xx001, which ignored the subclasses identified, e.g. 25033 was in subclass 25/1.
• Where numbers within a class became congested, it wasn't always possible to make the connection, e.g. locomotives in subclass 47/2 were fitted with Green Circle multiple-working equipment but retained their original numbers. In other cases it wasn't possible to start from xxxy01, e.g. subclass 08/9 started from 08991 because subclass 08/0 ran from 08001 to 08958.
• Because of the different arrangements for numbering multiple units (see above), subclasses may have no link to the unique identifier at all; this is especially true on the Southern Region. Sometimes, where there is a principal run of units and a small variant subclass, the majority will be subclass xxx/0 whatever their identifier, but the variant's subclass does reflect the identifier, e.g. Subclass 302/0 for the standard passenger units (302201-312) and 302/9 for the postal units (302990-302993).

So far as renumbering from the 1957 arrangements was concerned, most locomotives retained the last two digits of their number, though some classes were renumbered without reference to their previous numbers. This was usually where sub-classes had already been or were in the process of being created (for example classes 45 and 47, in which some members were being fitted with electric train heating equipment, and 86, subject to various modifications, mainly to the suspension). The other exception was if the first locomotive of a class had carried a number ending in "00" under the 1957 arrangements, because TOPS could not handle numbers ending in "00". These were either renumbered at the end of the class (e.g. the prototype class 50 D400 became 50050), or took a vacant number of another class member that had already been withdrawn (e.g. prototype class 24 D5000 became 24005, D5005 having been withdrawn in 1969), or were renumbered at the end of a sub-group within the class. Class 20 was particularly complicated in this respect. The class had been built in batches between 1957 and 1967 and all 228 members were still in service when the TOPS renumbering scheme was drawn up, but instead of class prototype D8000 being renumbered 20228 at the end of the class (which was not divided into sub-classes) it became 20050, displaced D8050 became 20128, and D8128 in turn became 20228.

The situation was different for multiple units. Where unit numbers were carried, they were usually three-digit already. TOPS simply prefixed these existing unit numbers with the newly allocated TOPS class number. The process was more complicated on the Southern Region, which used four-digit unit numbers and where a more general unit renumbering was required so that the first number of the unit coincided with the last digit of the class number. Many diesel multiple units were not kept in regular formations, so did not have existing unit numbers, and this situation was not changed under TOPS (except following refurbishment).

The TOPS system has been perpetuated by the privatisation of British Rail, though the allocation of classes and numbers appears to have become more random and less governed by the rules followed by British Rail (but even they made exceptions). See British Carriage and Wagon Numbering and Classification for an explanation of how TOPS applied also to carriages and wagons.

Please Note: This section explains the successful application of TOPS to multiple unit stock, the arrangement that persists today. However, there was an earlier attempt to apply TOPS that differed from the arrangement set out below. More details about the first arrangement may be found here.

In September 2011, the UK Rail Safety and Standards Board issued Railway Group Standard GM/RT2453,[4] which made some alterations to the TOPS classes allocated to various types of locomotive and multiple unit - primarily extending the number ranges for certain types of locomotives and multiple units where the previous allocation ranges were becoming exhausted. The standard also provided for the allocation of European Vehicle Numbers to most mainline rail vehicles in Britain, as part of the implementation of EC Directive 2008/57/EC (the Railway Interoperability Directive).

Railway Group Standard GM/RT2453 was replaced in December 2017 by Rail Industry Standard RIS-2453-RST,[5] which introduced the requirement for all new rail vehicles receiving authorisation to enter service in Britain after 1 January 2018 to display their full 12-digit European Vehicle Number regardless of whether or not the vehicle is intended for use only on domestic services.

Following the introduction of Standard RIS-2453-RST the allocation ranges have been as follows:

For further information on individual classes of locomotive or multiple unit, see these pages:

• List of Non-steam British Rail classes
• Steam locomotives of British Railways
• Locomotives of the Great Western Railway
• Locomotives of the Southern Railway
• Locomotives of the London, Midland and Scottish Railway
• Locomotives of the London and North Eastern Railway
• British electric multiple units
• British railcars and diesel multiple units

Related pages on BR numbering and classification include:

• British Rail TOPS first arrangement
• British Rail Regional Multiple Unit Numbering
• British Carriage and Wagon Numbering and Classification
• Route availability
• List of British Rail power classifications